module.exports = class circleFun {
    constructor(r) {
        this.r = r;
    }
    circumference() {
        return (Math.PI * this.r * 2).toFixed(1);
    }
    area() {
        return (Math.PI * this.r * this.r).toFixed(1);
    }
}
// https://blog.csdn.net/xqnode/article/details/60610885